Iceland Volcano: Greater Chance Of Dike Propagation And Volcanic Eruption In Coming Days -- Iceland Met Office

A picture taken on June 22 into the one crater that remained active until the end of the eruption that began on May 29. (Photo: Civil Defense)

Iceland Met Office

Updated 30 July at 13:30

• The number of earthquakes per day within the Sundhnúkur crater row is steadily increasing
• Model calculations suggest enough magma has now been recharged to the Svartsengi reservoir to trigger a new event
• There is an increased likelihood that this will occur within the next 7-10 days.
• Geodetic measurements show that the rate of uplift has decreased slightly during the past few days. This, along with the type of seismicity that was detected yesterday, are indicators that a dike propagation or a volcanic eruption may be imminent
• Hazard assessment remains unchanged from last week

Yesterday morning, increased microseismicity was detected within the Sundhnúkur crater row. The activity lasted for about 50 minutes and suggests that pressure within the system is increasing. Over the past 2 weeks, the number of earthquakes per day has been increasing.

Model calculations of volume change suggest that enough magma has been recharged to the Svartsengi reservoir to trigger a new event, with an increased likelihood of this occurring within the next 7-10 days.

Geodetic measurements show that the rate of uplift has decreased slightly during the past few days. This development coinciding with the earthquake activity measured yesterday in the Sundhnúkur crater row may be an indicator that a dike propagation and volcanic eruption is nearing.

Hazard assessment unchanged

The Icelandic Meteorological Office updated the hazard assessment considering the latest data. The hazard assessment is unchanged from last week and is valid until 6 August barring any developments.

The scenarios published by IMO on 23 July are also unchanged.

These are the scenarios that are considered most likely in the event of a volcanic eruption. Both scenarios are considered equally likely and assume that the initial vigor of the eruption will be similar to that of the eruption in May.

Scenario 1 - Eruption between Stóra-Skógfell and Sundhnúkur (central part of zone 3 on the hazard assessment map). Similar location to eruptions that began on 18 December 2023, 8 February, 16 March, and 29 May 2024.

• The likely precursor is a localized earthquake swarm between Stóra-Skógfell and Sýlingarfell, acceleration in deformation, and pressure changes in boreholes in the area.
• Very short pre-eruption warning time (less than 30 minutes).
• Lava could reach Grindavíkurvegur near Þorbjörn within 1.5 hours and Grindavíkurvegur near Svartsengi within 3 hours.

Scenario 2 - Eruption south of Sundhnúkur, near Hagafell, and extending south towards and potentially within northern Grindavík (southern part of zone 3 on the hazard assessment map and the northern part of zone 4). Similar location to the eruption that began on 14 January 2024.

• The likely precursor is an earthquake swarm starting near Stóra-Skógfell or Sýlingarfell and moving south, acceleration in deformation, and pressure changes in boreholes in the area.
• The warning interval for an eruption in this area would probably be longer than in scenario 1, but it is uncertain by how much. The length of the warning period depends on how far south the magma must break a pathway to the surface.
• Lava could reach Nesvegur and Suðurstrandarvegur within 1.5 hours. Lava flows could potentially close escape routes on land within about 6 hours.
• In this scenario, lava could reach the sea east of Grindavík within 1.5 to 3 hours. If lava reaches the sea, it could cause localized hazards due to rapid cooling of the lava. Initially, there would be a hazard due to ash and gas formation, primarily hydrochloric acid (HCl). Within a radius of about 500 meters from where the lava enters the sea, conditions would be life-threatening.
• A magma intrusion that reaches south of Hagafell will likely cause significant fault movements in Grindavík.
• There is a possibility that lava could erupt within Grindavík. One scenario is that lava erupting from a vent north of the protective barriers at Grindavík could flow into existing fissures and then re-emerge again within the town limits. Another scenario is the possibility of an eruptive fissure opening within Grindavík. However, in such a situation, it is likely that a fissure would first open north of the town before opening within the town limits.

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